Abrasive tools have diverse industrial uses, such as drilling cores, grinding stock to make machine parts, and cutting construction materials, such as brick, tile, metal and concrete. These tools generally include one or more abrasive elements secured to a cutting edge of a rigid, preferably metal, core. The abrasive elements of these tools often essentially consist of hard, finely divided particulates embedded in a bonding material. The bonding material, among other things, maintains the abrasive element in a shape that enables the abrasive particles to produce the desired cutting effect on the work piece.
Moderately hard abrasives such as aluminum oxide, silicon carbide and like, can be used to cut many materials. Very hard, so-called superabrasives, such as diamond and cubic boron nitride, are preferred to cut tough, i.e., extremely abrasive-resistant, materials such as concrete. The cost of tools containing superabrasives is normally quite high because the superabrasive component is very expensive. There has been considerable interest in developing abrasive tools which cut tough materials well, yet are less costly than tools in which the abrasive component is exclusively a superabrasive.
One approach to making better abrasive tools has been to incorporate both superabrasive and non-superabrasive particles in the abrasive element. In this fashion a tool containing the same total volume of abrasive, but less superabrasive, can cut as well as a more expensive, 100% superabrasive tool. U.S. Pat. Nos. 5,152,810 and 4,944,773, for example, teach that surprisingly advantageous results and a significantly lowered cost can be attained by replacing part of the superabrasive component with a sol-gel alumina abrasive. U.S. Pat. No. 5,443,418 represents an advance in this technology. It discloses an abrasive tool in which at least one superabrasive component and essentially uniformly oriented filamentary particles of a microcrystalline alumina are dispersed in a bond material.
It has been recognized, however, that the performance of the combined superabrasive/non-superabrasive type of tool involves a compromise between speed of cut and tool life. Speed of cut is a measurement of how fast a given tool cuts into a particular type of material. Tool life is the duration that the blade of the tool remains effective. Generally, fast cutting abrasive tools have shorter lives and longer lasting tools cut slowly.
Certain segmented abrasive tools with circumferentially differentiated abrasive segments to provide certain operational improvements have been disclosed. Japanese Patent Application No. Sho 55-105068 dated Aug. 1, 1980, teaches that stone cutting noise level can be reduced by interposing non-diamond abrasive regions circumferentially between diamond abrasive regions of a cutting wheel. International Patent Publication No. WO 92/01542 discloses a cutting tool that achieves different wear properties by varying grain size, type and concentration and bond type over the length of the cutter segment with respect to the direction of rotation of the cutting tool.
Recently certain high performance abrasive tools which are improved in both speed of cut and tool life have been developed. For example, U.S. Pat. No. 5,518,443 discloses an abrasive tool that achieves an improved combination of high cutting speed and long life by contacting the work piece with alternating regions of preferentially concentrated abrasive grains.
The modern technology for making high speed cutting tools without loss of tool life generally involves providing preferential concentrations of different abrasive components in geometrically intricate, defined zones within cutting segments. Unfortunately, the methods of making abrasive tools with different abrasive concentrations and bond types in an abrasive element are complex and costly. Additionally, the newer abrasive elements are somewhat delicate compared to traditional elements. Hence, abrasive elements constructed with zones of diverse abrasive and bond types are susceptible to at least partially disintegrate prematurely during manufacture and in use.
Accordingly, it is an object of the present invention to provide a low manufacturing cost, high performance, abrasive tool capable of cutting tough materials such as concrete, tile, masonry and metal. More particularly, it is an object to provide an abrasive tool for cutting tough materials which incorporates less volume concentration of superabrasive component than a comparatively effective, exclusively superabrasive-containing tool.
Another object of this invention is to provide safe, freely-cutting, faster cutting, longer life cutting performance through an abrasive tool design that contains a plurality of discretely defined zones of different abrasive compositions in each abrasive segment.
Still another object of the present invention is to provide a high performance abrasive tool for tough materials which is simple, quick and inexpensive to produce despite having multiple zones of different types, concentrations and sizes of abrasive grains and bond materials in each abrasive segment.
A further object of this invention is to provide a facile method for producing abrasive segments for a high performance abrasive tool.
Yet another object of the present invention is to provide a structurally strong, multiple zoned abrasive segment capable of being produced and assembled into a high performance abrasive tool with less breakage than was heretofore available.
Due to the enhanced integrity and to the expeditious manufacturing method involved, it is expected that the novel tool can be made with superior productivity. That is, compared to conventional manufacture of intricately constructed abrasive tools, the energy and materials consumed to produce each tool and the unit rate of production will be improved. Therefore, a still further objective of this invention is to provide a high performance, tough-cutting abrasive tool which appreciably reduces the overall cost of a cutting task.
Accordingly, there is now provided a crenelated shaped abrasive segment exceptionally well suited to cut a wide variety of tough materials encountered in industry. The novel abrasive segment having an operative perimeter comprising
a length along the operative perimeter; PA1 an inner face separated by a segment width from an outer face substantially parallel to the inner face to define sides of the abrasive segment along the operative perimeter; PA1 a vein comprising a primary abrasive and a first bond material, the vein extending continuously and completely along the length of the abrasive segment and transversing the segment width at least once to coincide alternately with a portion of each of the inner and outer faces to define longitudinal vein parts of substantially uniform vein width less than the segment width, and a transverse vein part connecting consecutive longitudinal vein parts; and PA1 a plurality of separated abrasive regions between the inner and outer faces and the vein comprising a second bond material.
Also according to this invention there is provided an abrasive tool comprising at least one, and preferably a plurality of crenelated abrasive segments attached to a rigid core. The crenelated abrasive segments can be employed advantageously to provide core drill bits, rotary reciprocating saw blades, and other abrasive tools.
There is further provided a method for making crenelated abrasive segments and a method making abrasive tools which includes attaching crenelated abrasive segments to a core.